/Engine/Plugins/Online/OnlineSubsystem/Source/Public/Interfaces/OnlineChatInterface.h
Check if a message is from the local user
true if the message is from the local user, false if not
bool IsMessageFromLocalUser ( const [FUniqueNetId](API\Runtime\CoreOnline\Online\FUniqueNetId) & UserId, const [FChatMessage](API\Plugins\OnlineSubsystem\Interfaces\FChatMessage) & Message, const bool bIncludeExternalInstances )